1. Technical Field
This invention relates to a coreless motor suitable for use as a driving force of precision equipment.
2. Description of the Prior Art
A small-sided motor used as an actuator for precision equipment has conventionally contained a coreless motor in which a coil circulates around a magnet. Its merits are that it is free from reluctance torque that occurs in a cored motor (motor with an iron core), that commutation sparks are few and electric noise is little and that the rotor inertia is small and responsiveness is resultantly excellent, among other characteristics.
It is a matter of course that a motor to be used as a driving force for precision equipment must be excellent in responsiveness and controllability. In the case of precision equipment having many motors, furthermore, each motor is required to consume little electric power and to have high energy efficiency.
Although the conventional coreless type motor is excellent in responsiveness and controllability, it also has a shortcoming of not necessarily being characterized by high energy efficiency for the reasons shown below.
The conventionally used coreless motor is of the type in which a cylindrical-form coil is revolved in a gap between a magnet and a coil yoke, but rotating torque working on the said coil arises in the direction that constitutes a right angle with the lead wire composing the coil; as such, if the direction of the lead wire composing the coil (direction of wiring) is arranged to be in a right direction with the coil revolution circumference direction, the rate of rotating torque (rotational output) in relation to the strength of a magnetic field formed by the coil will rise, so that a motor featuring high energy efficiency can be obtained.
However, a cylindrical-form is so composed that the lead wire constituting the coil is not wound to be in parallel with the elevated height of the coil but designed to have some degree of inclination angle, such that the inclination angle becomes larger, the rotating torque working on the magnet reduces, lowering energy efficiency.
If the axis direction length is tried to be shortened in such a motor, therefore, the angle formed by the coil winding direction with the coil axis direction will become larger, and energy efficiency will accordingly decline further, which poses a barrier in realizing small-sized high-efficiency motor.